docs: def _get_openstack_release(self):
          """Get openstack release.
  
             Return an integer representing the enum value of the openstack
             release.
             """
          # Must be ordered by OpenStack release (not by Ubuntu release):
          for i, os_pair in enumerate(OPENSTACK_RELEASES_PAIRS):
              setattr(self, os_pair, i)
  
          releases = {
              ('trusty', None): self.trusty_icehouse,
              ('trusty', 'cloud:trusty-kilo'): self.trusty_kilo,
              ('trusty', 'cloud:trusty-liberty'): self.trusty_liberty,
              ('trusty', 'cloud:trusty-mitaka'): self.trusty_mitaka,
              ('xenial', None): self.xenial_mitaka,
              ('xenial', 'cloud:xenial-newton'): self.xenial_newton,
              ('xenial', 'cloud:xenial-ocata'): self.xenial_ocata,
              ('xenial', 'cloud:xenial-pike'): self.xenial_pike,
              ('xenial', 'cloud:xenial-queens'): self.xenial_queens,
              ('yakkety', None): self.yakkety_newton,
              ('zesty', None): self.zesty_ocata,
              ('artful', None): self.artful_pike,
              ('bionic', None): self.bionic_queens,
              ('bionic', 'cloud:bionic-rocky'): self.bionic_rocky,
              ('bionic', 'cloud:bionic-stein'): self.bionic_stein,
              ('cosmic', None): self.cosmic_rocky,
              ('disco', None): self.disco_stein,
          }
          return releases[(self.series, self.openstack)]